In a media distribution environment, one or more source devices communicate media content to one or more receiving devices. In this environment, it is important for the source devices and the receiving devices to have synchronized clocks. Synchronizing source and receiving clocks is important, for example, to maintain synchronization between the audio and video data presented by the receiving devices. If the audio and video data is not synchronized, the audio data will not be presented at the correct time with respect to the video data. For example, if the audio and video data is not synchronized, the movement of a person's lips presented from the video data may not correspond to the spoken word(s) presented from the audio data. The audio presentation may appear to be “ahead of” or “behind” the video presentation.
Some media distribution environments include a time synchronization protocol that allows source devices and receiving devices to exchange clock information. An example time synchronization protocol may be provided via the MPEG-2 (Moving Picture Experts Group) system layer, which defines transport streams and program streams. However, other media distribution environments do not utilize a time synchronization protocol. In particular, certain networked media playback systems do not use a time synchronization protocol. These systems need to maintain synchronization between the source device clock and the receiving device clock without the benefit of a time synchronization protocol.